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Praseodymium in the formal +5 oxidation state

Nature Chemistry volume 17, pages 1005–1010 (2025)Cite this article

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Abstract

Praseodymium in the +5 oxidation state is a long-sought connection between lanthanide, early-transition and actinide metal redox chemistries. Unique among the lanthanide series, evidence for molecular pentavalent praseodymium species has been observed in the gas phase and noble gas matrix isolation conditions. Here we report the low-temperature synthesis and characterization of a molecular praseodymium complex in the formal +5 oxidation state, [Pr5+(NPtBu3)4][X−] (where tBu = tert-butyl and X− = tetrakis(pentafluorophenyl)borate or hexafluorophosphate). Single-crystal X-ray diffraction, solution-state spectroscopic, solution magnetometric, density functional theory and multireference wavefunction-based methods indicate a highly multiconfigurational singlet ground state. An inverted ligand field drives this unique electronic structure, which establishes a critical link in understanding the bonding of high-valent metal complexes across the periodic table.

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Fig. 1: Synthesis and solution characterization of 1.
Fig. 2: Structure and electronic absorption spectra of 3.
Fig. 3: MOs of 1M+.
Fig. 4: π orbital sets for 3.

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Data availability

The data that support the findings of this study are available from the main text and the Supplementary Information. X-ray data are available free of charge from the Cambridge Crystallographic Data Centre under references 2381100 (3b) and 2381101 (3a). Additional spectroscopic, crystallographic and computational data are included in the supplementary materials. Computational coordinates and energies and source data generated during the current study have been deposited in the figshare database (https://doi.org/10.6084/m9.figshare.26894113). Source data are provided with this paper.

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Acknowledgements

The experimental work was supported by a National Science Foundation (NSF) CAREER grant under award number CHE-1943452 (A.C.B., H.T. and H.S.L.P.). H.S.L.P. is an Alfred P. Sloan Research Fellow. The computational work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Element Chemistry Program, under award number DE-SC0025311 (S.R.C. and B.V.). I.A.P. acknowledges the start-up funds and Meyer Early Career Launch Fellowship at Washington State University. Computations supporting this project were performed on high-performance computing systems at the University of South Dakota, funded by NSF award OAC-1626516 (S.R.C. and B.V.) and using the computational resources at the Ohio Supercomputer Center and the ARCC HPC cluster at the University of Akron (C.M.S. and I.A.P.).

Author information

Authors and Affiliations

  1. School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, USA

    Andrew C. Boggiano, Julie E. Niklas, Haruko Tateyama, Hongwei Wu, Johannes E. Leisen & Henry S. La Pierre

  2. Department of Chemistry, The University of Akron, Akron, OH, USA

    Chad M. Studvick

  3. Department of Chemistry, The University of South Dakota, Vermillion, SD, USA

    Sabyasachi Roy Chowdhury & Bess Vlaisavljevich

  4. Department of Chemistry, The University of Iowa, Iowa City, IA, USA

    Sabyasachi Roy Chowdhury & Bess Vlaisavljevich

  5. Institut für Anorganische Chemie, RWTH Aachen University, Aachen, Germany

    Florian Kleemiss

  6. Department of Chemistry, Washington State University, Pullman, WA, USA

    Ivan A. Popov

  7. Nuclear and Radiological Engineering and Medical Physics Program, School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA

    Henry S. La Pierre

  8. Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA

    Henry S. La Pierre

Authors
  1. Andrew C. Boggiano
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Contributions

A.C.B. and H.S.L.P. conceived the idea presented in this publication. H.S.L.P., I.A.P. and B.V. supervised the project and acquired funding. A.C.B., H.T. and H.S.L.P. developed the syntheses. A.C.B., J.E.L. and H.W. performed the spectroscopic and electrochemical characterization and analysis. A.C.B., J.E.N. and F.K. performed the crystallographic characterization. C.M.S., S.R.C., B.V. and I.A.P. performed the theoretical calculations and analysis. Analysis and visualization were performed by A.C.B., J.E.N., C.M.S., S.R.C., F.K., I.A.P., B.V. and H.S.L.P. The first draft was written by A.C.B., J.E.N., C.M.S. and S.R.C., with contributions from all authors. The paper was reviewed and edited by H.S.L.P., I.A.P. and B.V. with input from all authors.

Corresponding authors

Correspondence to Bess Vlaisavljevich, Ivan A. Popov or Henry S. La Pierre.

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Nature Chemistry thanks Nicholas Chilton, Stephan Hohloch and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 α-spin MO energy diagrams for 4, 1, and 1M+.

AO contributions specified by yellow (Pr) and blue (ligands) fractions in the MO horizontal bars and electrons residing in the occupied MOs (OMOs) by vertical gray lines. The highest occupied ligand-dominant orbital in each complex is shifted to 0 eV for comparison. The extended black box points out eight OMOs describing Pr–N π interactions across the complexes, with the corresponding average Pr AO contributions shown above. The dashed boxes display two lowest unoccupied MOs (UMOs), with the corresponding average Pr AO contributions shown below. Orbital energy degeneracy is set to 0.05 eV to aid visualization. Full unperturbed MO diagrams are depicted in Supplementary Figs. 84–86.

Extended Data Table 1 Spin-lattice relaxation times (T1) from solution inversion recovery NMR measurements in THF-d8 at –50 °C
Full size table

Supplementary information

Supplementary Information

Materials, Supplementary Text, Figs. 1–95 and Tables 1–23.

Supplementary Data 1

Crystallographic data for compound 3a (CCDC 2381101).

Supplementary Data 2

Crystallographic data for compound 3b (CCDC 2381100).

Source data

Source Data Fig. 1

Referenced cyclic voltammetry data.

Source Data Fig. 2

Source UV–vis data.

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Boggiano, A.C., Studvick, C.M., Roy Chowdhury, S. et al. Praseodymium in the formal +5 oxidation state. Nat. Chem. 17, 1005–1010 (2025). https://doi.org/10.1038/s41557-025-01797-w

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